EP1584134B1 - Method for reducing common-mode interference currents in an electric drive system, and corresponding electric drive system - Google Patents

Description

Method for reducing common-mode parasitic currents in an electric drive system and corresponding electric drive system.

The invention relates to a method according to the preamble of patent claim 1 and an electric drive system according to the preamble of patent claim 6; It is assumed that an electric drive system with a DC voltage supply device, as for example by the EP 0 334 112 B1 is known.

In accordance with the state of the art, pulse converters fed by a DC power supply allow the operation of a rotating field machine, such as a rotary field machine. a synchronous machine, with variable frequency and voltage. Since both the individual winding phases of a rotating field machine as well as the DC voltage supply device have not negligible parasitic Ableitkapazitäten against ground potential ("earth capacitances"), resulting from the switching operations of the semiconductor switches of the pulse converter capacitive Umladeströme, which then in the DC voltage supply device as EMC interference in Form common-mode interference currents. On the one hand, these interference currents can disturb other devices that are galvanically connected to the DC power supply ("line-connected EMC fault"). On the other hand, they additionally lead to a z.T. considerable radiation of radio interference fields and can then also disturb devices that have no galvanic connection to the DC power supply ("RFI EMI interference"). Therefore, strict limits for the permissible common-mode interference currents are generally prescribed.

Particularly strict limits apply in such systems and systems, where on the one hand large spatial dimensions of the DC power supply device, large spatial Extension of the galvanically connected line network and high electrical power coincide on the other hand with tight spatial conditions, small possible distances to potentially interference-prone devices with application-related high electrical and electromagnetic sensitivity. Such boundary conditions occur, for example, in ships with an electric propulsion propulsion system, especially in submarines.

High power field machines, in particular marine propulsion engines, are, as in the EP 0 334 112 B1 shown often fed via multiple pulse inverters from a common DC power supply. To avoid high compensation currents in the winding phases due to mutual magnetic coupling, the switching operations of the individual pulse inverters are synchronized with each other, ie they take place almost simultaneously. The pulse converters are therefore clocked with essentially the same switching frequency. Due to the simultaneity of the switching operations in the individual pulse converters, however, the charging and discharging current pulses of the individual pulse converters caused by the earth capacitances of the winding phases add up and a high common-mode interference current flows in the voltage supply device.

Various methods are known for reducing the common mode currents caused by the pulse inverter feed and the resulting disturbances. They aim to increase the impedances effective for the common-mode parasitic currents by inserting suitable additional inductances at a suitable location in accordance with this objective. So is by the DE 100 59 332 A1 It is known to transformer-feed an impedance into all motor connection lines leading to a motor, for example by passing all motor connection lines through a magnetizable coupling core. However, such coupling cores have considerable weight and volume, especially in large power drives on and their installation in a drive device can therefore be problematic especially in tight spaces. In addition, this solution can represent a considerable financial expense. From the DE 100 40 851 A1 It is known to insulate the winding-carrying components of the electrical machine relative to the housing and to couple the winding-carrying parts via an inductance to the housing ground. This additionally required inductance is then in series with the parasitic capacitance of the windings against ground potential and thus also increases the decisive impedance for the common-mode currents.

DE 100 43 934 A1 discloses a control module for a bridge converter for commutating currents for an electric motor. The bridge converter has at least three bridge branches supplied by a DC voltage intermediate circuit, each having an upper switch and a lower switch and one tap arranged between the respective upper and lower switch for applying an output voltage to a respective motor winding of the electric motor. The control module controls the switches with pulse generator means for forming switching pulses such that in each case at least one bridge branch is inactive, while in each case two further bridge branches are active in pairs and operate essentially in push-pull.

EP 0 898 359 A2 discloses an inverter having a plurality of inverter bridges whose output voltages are summed via a transformer having a number of primary windings and associated secondary windings corresponding to the number of inverter bridges and a center tap grounded via a ground connection. For attenuation or suppression of flowing through the ground connection in-phase or common-mode noise currents within the transformer, the secondary windings are each divided into a first and second similar sub-secondary winding and the sub-secondary windings are among themselves and connected to the center tap, the common mode voltages induced in the sub-secondary windings cancel each other out.

In view of this prior art, the present invention seeks to reduce the common-mode interference currents without the use of additional inductance-related components and to save the costs associated with the use of additional inductances costs and expenses for space, weight, installation and wiring.

The solution of this object is achieved starting from a method according to the preamble of claim 1 or an electric drive system according to the preamble of claim 5 by the characterizing teaching. Advantageous embodiments of the method according to claim 1 are the subject of the dependent claims 2 to 4; advantageous embodiments of the electric drive system according to claim 5 are the subject of the dependent claims 7 to 14.

By means of the method according to the invention or the electrical drive system according to the invention, it is achieved that the common mode interference currents generated by the two pulse converters are oppositely directed against one another via the parasitic capacitances of the windings and thus largely cancel one another, in particular in the DC voltage supply device.

By the solution according to the invention, the relevant for the drive function of the induction machine output voltages of the pulse converter, i. the differential voltages between the output terminals of each inverter, unchanged. The reduction of the common mode interference currents takes place solely by appropriate control of the pulse converter. Special components, such as Additional inductances are not needed. Thus, savings in costs and expenses for space requirements, weight, installation and wiring are achieved compared to a use of additional inductances.

The solution according to the invention and its embodiments are equally suitable for single-phase induction machines via single-phase converters, as well as for machines with polyphase, e.g. Three-phase winding systems and power supply via multi-phase inverters.

The common-mode interference currents generated by the two pulse converters fed from the same DC voltage supply device cancel each other out particularly well if they have approximately the same time course and amplitude when the direction is opposite to one another. In the case of a three-phase machine with several, in the sense of a single-strand feeding of a single-phase pulse inverter supplied winding strands and assuming the same size parasitic winding capacitances of the individual winding strands, this can be achieved by each of the two pulse converters are controlled by the control device such that the instantaneous values the output voltages of each two pulse inverters are at least approximately equal. In the case of a three-phase machine with several winding systems fed by a multi-phase pulse converter, this can be achieved by arranging the winding systems fed by the two pulse converters at least approximately 180 ° offset from one another in the induction machine and the two pulse converters each by the control device so be controlled so that the instantaneous values of the output voltages of each two pulse inverters are inverse to each other.

If there are differences in the momentary values of the modulation and thus differences in the switching times and the output voltages of the two pulse converters, as the e.g. is the case at different fundamental phase shifts in the different phase windings of a rotating field machines, residues remain in the resulting common mode noise. It is therefore particularly advantageous to arrange the pairs of pulse converters preferably according to this criterion, i. they e.g. identical or close to each other lying fundamental phase positions of the output voltages. In induction machines having a high number of winding phases, e.g. are used in propeller drives in submarines, these conditions are given.

Measurements on a drive system according to the invention in accordance with the drive system with single-strand feeding of the machine windings via pulse converters have shown that the common-mode interference currents are exceeded by more than a factor of 10 by the design of the drive according to the invention, in particular the control of the pulse converters according to the invention. reduce by more than 20 dB.

With regard to the generation of the drive pulses resulting in a realization of the solution according to the invention no restrictions, so that the control or modulation of the pulse converter advantageously both with online-working modulation method (eg sine-delta modulation, space vector modulation, etc.) as well as offline working modulation method. e.g. offline calculated pulse patterns, can be done.

A particularly simple, clear and advantageous embodiment of the solution according to the invention results when used a modulation by means of a triangular auxiliary function in the sense of a sine-wave modulation, wherein the triangular auxiliary function of one of the two pulse inverters in relation to the triangular auxiliary function of the other of the two pulse inverters is inverted. The use of this modulation is particularly advantageous because it can be done in a particularly advantageous embodiment using a programmable hardware device, in particular LCA; or if this is not possible or not desired, can be realized in an advantageous manner with conventional hardware in analog and / or digital technology.

A good synchronization of the drive pulses of the two each fed from a common DC power supply pulse converter can be ensured by a common control device is provided for each two pulse converters.

Is it not possible for structural or other reasons that both fed from a common DC power supply pulse converters receive their drive pulses from a common control device, the result is a further advantageous embodiment of the invention in that several, especially two, device technology and / or functional separate and appropriately signal-technically linked together, in particular synchronized with each other, driving devices are provided for each of two pulse converters.

In an advantageous embodiment of the electric drive system according to the invention, the DC voltage supply device and / or belonging to the DC voltage supply device current and voltage-carrying electrical conductors and / or to the DC voltage supply device belonging DC voltage sources has a large spatial extent and / or distribution and thus allows the power supply spatially remote drive components with low common-mode parasitic currents.

The electric drive system according to the invention can be used in a particularly advantageous manner in an electrical vehicle electrical system, in particular an electrical DC on-board electrical system on ships, in particular on submarines, since there are particularly high demands on the common mode interference currents in such on-board networks.

The electric drive system according to the invention can be designed with one or more electric induction machines, which are designed as synchronous machines with electrical or permanent magnetic excitation or as asynchronous machines.

FIG 1

eine vereinfachte Darstellung einer Schaltung zur Speisung von zwei Wicklungssträngen einer Drehfeldmaschine über zwei einphasige Pulsumrichter aus einer gemeinsamen DC-Spannungsversorgungseinrichtung;

FIG 2

mit Bezug auf FIG 1 Zeitdiagramme des Verlaufs der Pulsumrichter-Ausgangsspannungen, wobei entsprechend der erfindungsgemäßen Lösung beide Umrichter so angesteuert werden, dass sich die von beiden Umrichtern erzeugten Common-Mode-Störströme über die parasitären Kapazitäten des Wicklungsstränge gegenüber Erdpotential gegeneinander aufheben;

FIG 3

eine vereinfachte Darstellung einer Schaltung zur Speisung von zwei dreisträngigen Wicklungssystemen einer Drehfeldmaschine über zwei dreiphasige Pulsumrichter aus einer gemeinsamen DC-Spannungsversorgungseinrichtung ;

FIG 4

mit Bezug auf FIG 3 Zeitdiagramme des Verlaufs der Pulsumrichter-Ausgangsspannungen, wobei entsprechend der erfindungsgemäßen Lösung beide Umrichter so angesteuert werden, dass sich die von beiden Umrichtern erzeugten Common-Mode-Störströme über die parasitären Kapazitäten der Wicklungssysteme gegenüber Erdpotential gegeneinander aufheben;

FIG 5

eine vereinfachte Darstellung einer Schaltung zur Speisung eines Wicklungsstranges einer Drehfeldmaschine über einen einphasigen Pulsumrichter aus einer DC-Spannungsversorgungseinrichtung;

FIG 6

mit Bezug auf FIG 5 Zeitdiagramme des Verlaufs der Umrichter-Ausgangsspannungen, die für die Entstehung des Common-Mode-Störstromes über die parasitären Kapazität des Wicklungsstranges gegenüber Erdpotential maßgeblich sind.

The invention, as well as further advantageous embodiments of the invention according to features of the subclaims, will be described below with reference to embodiments in the FIGS. 1 to 4 explained in more detail; the problem underlying the invention is based on the Figures 5 and 6 explained. For a better understanding of the solution according to the invention simplified representations are used in the figures. As an example of a suitable modulation or drive method, a formation of the drive signals is represented by means of a triangular auxiliary function in the sense of sine-delta modulation. The simplifications used in the figures also relate to the relevant for the formation of the common-mode currents parasitic capacitances to earth potential, which are simplified in the form of concentrated, capacitive circuit elements, that is represented in the form of capacitors. The embodiments illustrated in the figures and associated explanations thus serve merely to explain the invention and are not restrictive of these. Show it:

FIG. 1

a simplified representation of a circuit for feeding two winding phases of a rotating field machine via two single-phase pulse converter from a common DC voltage supply device;

FIG. 2

regarding FIG. 1 Time diagrams of the course of the pulse converter output voltages, according to the solution according to the invention, both converters are controlled so that the common mode interference currents generated by both converters cancel each other over the parasitic capacitances of the winding strands against ground potential;

FIG. 3

a simplified representation of a circuit for feeding two three-phase winding systems of a rotating field machine via two three-phase pulse converter from a common DC voltage supply device;

FIG. 4

regarding FIG. 3 Time diagrams of the course of the pulse converter output voltages, according to the solution according to the invention, both inverters are driven so that the common mode interference currents generated by both converters cancel each other over the parasitic capacitances of the winding systems against ground potential;

FIG. 5

a simplified representation of a circuit for feeding a winding strand of a rotating field machine via a single-phase pulse converter from a DC voltage supply device;

FIG. 6

regarding FIG. 5 Timing diagrams of the course of the inverter output voltages, which are decisive for the generation of the common-mode interference current via the parasitic capacitance of the winding branch with respect to ground potential.

Based FIG. 5 and 6 should first be explained the problems underlying the invention. The outline sketch of FIG. 5 shows a winding section 31 of a rotary field machine 3, which is fed via a pulse converter 1 from a DC voltage supply means 4. The voltage supply device 4 includes the DC voltage source 40 and the current and voltage-carrying conductors 41 with positive potential UDC + and 42 with negative potential UDC-, via which the supply of electrical energy to the pulse converter 1 takes place.

The single-phase pulse converter 1 in FIG. 5 has two half-bridges W1a and W1b, each with two switches S1a, S1a 'and S1b, S1b'. By means of a suitable drive device 51, the switches S1a, S1a 'and S1b, S1b' are driven so that a desired voltage U1 is established at the output terminals 1a and 1b of the pulse converter 1 and thus at the winding strand 31 of the rotary field machine 3 connected thereto. The pulse converter output voltage U1 thereby arises as the differential voltage of the output potentials U1a and U1b of the two half bridges W1a and W1b. The parasitic capacitance of the winding strand 31 with respect to ground potential is shown for simplicity by the capacitor Cp31. The capacitor Cp4 represents, in a simplified manner, the parasitic capacitance of the DC voltage supply device 4 against ground potential. The voltage Uc31 denotes the voltage drop across the parasitic capacitance Cp31 of the winding strand 31 with respect to ground potential.

In FIG. 6 are for the in FIG. 5 shown circuit shows the timing of the relevant pulse converter output voltages. The actuation of the switches S1a, S1a 'and S1b, S1b' takes place in an exemplary manner with the aid of a triangular auxiliary function UΔ1 in the sense of the known sine-triangle modulation. In this case, in the known manner in the drive device 51, a triangular auxiliary function UΔ1 is compared with a control voltage Ust1 and -Ust1 determining the pulse converter output in order to determine therefrom the switching times for the switches S1a, S1a 'and S1b, S1b'.

How out FIG. 5 and FIG. 6 Furthermore, it can be seen from the time characteristic of the voltage Uc31 over the parasitic capacitance Cp31 that this voltage Uc31 changes periodically as a function of the output potentials U1a and U1b. For example, in the time intervals ta, the entire winding strand 31 is at negative potential UDC- of the DC voltage supply device and in the time intervals tb is at positive potential UDC + of the DC voltage supply device. This is associated with a periodic, dependent on the time course of the voltage Uc31 reloading the earth capacitance Cp31 with corresponding charging or recharging Icm1. In each case caused by the pulse inverter 1 voltage change of Uc31 thus flows via Cp31 a noise current Icm1 whose circuit closes over ground and the parasitic capacitance Cp4 back to the DC voltage supply device 4 and there is effective as common mode noise.

Based FIG. 1 and 2 Now, the reduction according to the invention of the common-mode interference currents will be explained using the example of an electric drive system with a single-phase feed of a three-phase machine via a single-phase pulse converter. FIG. 1 shows a simplified representation of an electric induction machine 3 with two phase windings 31, 32, which are fed via a respective single-phase pulse converter 1, 2 from a common DC voltage supply means 4. Both pulse converters 1, 2 are operated with the same modulation and generate at their output terminals 1a, 1b and 2a, 2b at least approximately the same output voltages U1 and U2.

As FIG. 1 shows, the pulse inverters 1 and 2 each have the same basic circuit, that of the pulse converter 1 of FIG. 5 equivalent. Each of the pulse converters 1, 2 points in this case, according to the pulse converter 1 of FIG. 5 , two half bridges W1a, W1b or W2a, W2b each with two switches (S1a, S1a 'and S1b, S1b' or S2a, S2a 'and S2b, S2b'). In order to avoid high equalizing currents between the individual, via the respective pulse converters 1, 2, winding strands 31, 32, the pulse inverters 1, 2 are clocked with substantially the same switching frequency, so that the switching operations in the pulse converters 1, 2 take place almost simultaneously. With regard to the further description of the circuit and function of the pulse converter 2 is to the description of pulse converter 1 of FIG. 5 referenced; the reference numbers are adapted functionally and meaningfully.

The pulse converter 1 generates-as already described-due to its switching operations and the associated changes in its output potentials U1a, U1b at the earth capacitance Cp31 of the winding section 31 fed by it, a voltage drop Uc31 and thus a common-mode interference current Icm1 in the DC voltage supply device 4. Accordingly, due to its switching operations and the associated changes in its output potentials U2a, U2b, the pulse converter 2 causes a voltage drop Uc32 at the earth capacitance Cp32 of the winding section 32 fed by it, and thus a common mode interference current Icm2 in the DC voltage supply device 4 Thus, a total common-mode interference current Icmg, which results from the sum of the common-mode interference currents Icm1 and Icm2 of the two individual pulse converters 1 and 2, becomes effective for the DC voltage supply device 4: Icmg = Icm1 + Icm2.

In a symmetrical structure of the induction machine 3 and the parasitic winding capacitances Cp31, Cp32 of the winding strands 31, 32 are at least approximately the same size, so that at equal voltages Uc31 and Uc32 and the two common-mode interference currents Icm1 and Icm2 are equal. According to the invention, the two pulse converters 1, 2 are driven by drive devices 51, 52 in such a way that both pulse converters 1, 2 have their outputs 1a, 1b and 2a, respectively, to reduce the total common-mode interference current Icmg active in the DC voltage supply device 4 2b, the potentials U1a, U1b or U2a, U2b which are decisive for the formation of the common mode currents Icm1, Icm2, are connected at least approximately simultaneously to the winding phases 31, 32 of the induction machine 3 such that the voltage potentials Uc31, Uc32 are applied via the parasitic Capacities Cp31, Cp32 of the winding strands 31, 32 are directed opposite to earth potential and thus cancel the common mode interference currents Icm1 and Icm2 against each other. For this purpose, the two drive devices 51, 52 are connected to one another in a suitable manner by signal technology, in particular synchronized with one another.

If spatial, functional or technical equipment conditions permit, a common control device 5 can be provided instead of the synchronized drive devices 51, 52.

FIG. 2 shows on the basis of time diagrams an example of the course of the pulse inverter output potentials U1a, U1b or U2a, U2b and the resulting pulse converter output voltages U1, U2 and the voltages Uc31, Uc32 on the parasitic capacitances Cp31, Cp32. By driving the half-bridge W1a of the inverter 1 in the opposite direction to the half-bridge W2b of the inverter 2 and driving the half-bridge W1b of the inverter 1 in opposite directions to the half-bridge W2a of the inverter 2 is achieved that the output potential U1a in opposite directions to the output potential U2b and the output potential U1b in opposite directions to the potential U2a changes. In the time intervals ta, the entire winding strand 31 is thus at negative potential UDC- of the DC voltage supply device 4, d, h. Uc31 = UDC- = U1a = U1b. The entire winding strand 32, however, is in the time period ta at positive potential UDC + the DC voltage supply device 4, ie Uc32 = UDC + = U2a = U2b. In the time intervals tb, the entire winding strand 31 is at positive potential UDC + of the DC voltage supply device 4, d, h. Uc31 = UDC + = U1a = U1b and the entire winding phase 32 is in the time interval tb at negative potential UDC- the DC voltage supply device 4, ie Uc32 = UDC- = U2a = U2b. Thus, the voltage changes over the parasitic capacitances Cp31 and Cp32 run in opposite directions to each other, as in FIG. 2 can be seen on the basis of the time profiles of the voltages Uc31 and Uc32 and is also clear from the sum of the two voltages Uc31 + Uc32, which is zero at all times.

Under the conditions of simultaneous switching operations in the converter half-bridges W1a, W2b or W1b, W2a and equally large capacitances Cp31 and Cp32, the common-mode currents Icm1 and Icm2 flowing through ground potential thus have the same magnitude, but are oppositely directed, i. Icm1 = -Icm2. In sum, both currents Icm1 and Icm2 cancel each other out, i.e., they are canceled. In the DC voltage supply device 4, therefore, no common-mode interference current Icmg originating from the switching operations of the pulse converters 1, 2 becomes more effective.

Of particular importance for the behavior of the electric induction machine 3 is that the voltage applied to the winding phases 31, 32 inverter output voltages U1, U2 of the two pulse inverters are not changed 1.2 and continue to have the same time course, so that There is no change for the function of the drive.

The activation of the pulse converters 1, 2 can, as already in connection with the explanations to FIG. 5 and 6 represented, for example, with the aid of a triangle auxiliary function UΔ in the sense of the known sine-wave modulation done. As FIG. 2 shows the opposite direction control of the half-bridge W1a of the inverter 1 to the half-bridge W2b of the inverter 2 and the opposite direction control of the half-bridge W1b of the inverter 1 to the half-bridge W2a of the inverter 2 is achieved in that in the drive device 51 is a triangular auxiliary function UΔ1 = UΔ and in the drive device 52, the inverse triangular auxiliary function UΔ2 = -UΔ is used. In the schematic diagram of the embodiment of FIG. 1 the triangular auxiliary function UΔ2 = -UΔ is generated from the triangular auxiliary function UΔ with the aid of the symbolically represented inverter 59. The control voltage Ust determining the converter output is preferably identical for both pulse converters 1, 2, Ust1 = Ust2 = Ust, so that the instantaneous values of their output voltages U1, U2 are at least approximately equal.

Based FIG. 3 and 4 Now, the reduction according to the invention of the common-mode interference currents will be shown using the example of an electric drive system with feeding of two three-phase winding systems of a rotating field machine via two three-phase pulse converters from a common DC voltage supply device.

FIG. 3 shows a simplified representation of two winding systems 33, 34 of a rotary electric machine 3, which are fed via a respective three-phase pulse converter 1, 2 from a common DC voltage supply means 4. The three phases are marked with the letters a, b, and c. The DC voltage supply device 4 in turn comprises a DC voltage source 40 and current and voltage-carrying conductors 41, 42, as already explained in the explanations FIG. 1 and 5 are described. Cp4 again denotes the parasitic capacitance of the DC voltage supply device against ground potential. The pulse converters 1 and 2 each have three half-bridges W1a, W1b, W1c or W2a, W2b, W2c, each with two switches (S1a, S1a ', S1b, S1b', S1c, S1c 'and

S2a, S2a '; S2b S2b '; S2c, S2c '). At the output terminals 1a, 1b, 1c and 2a, 2b, 2c of the inverter 1 and 2, the two winding systems 33 and 34 of the induction machine 3 are connected. The parasitic capacitances of the winding strands against ground potential are shown in a simplified manner in the form of parasitic capacitances Cp33, Cp34 of the winding systems 33, 34 against ground potential. The voltage drop across the parasitic capacitance Cp33 is designated Uc33; the voltage across the capacitor Cp34 is called Uc34.

The two winding systems 33, 34 of the rotary field machine 3 according to the invention are arranged offset by 180 ° to each other electrically. With the same winding sense of the motor windings, this can be done by suitable interconnection of the winding starts or winding ends of the winding strands 33a, 33b, 33c and 34a, 34b, 34c. For clarity, in FIG. 3 the winding starts with the same winding direction as usual marked by a dot ●.

For reasons of high clarity of the solution according to the invention, a driving method using triangular auxiliary functions in the sense of the known sine-wave modulation is again used in the example shown here for the purpose of controlling the pulse converter ,

Due to its switching operations and the associated changes in its output potentials U1a, U1b, U1c, the pulse converter 1 generates a voltage drop Uc33 at the earth capacitance Cp33 of the winding system 33 fed by it and thus a common mode interference current Icm1. Accordingly causes the pulse converter 2 due to its switching operations and the associated changes in its output potentials U2a, U2b, U2c at the earth capacitance Cp34 of the winding strand 34 fed by it, a voltage drop Uc34 and so that a common-mode interference current Icm2. Thus, in the DC voltage supply device 4, a total common-mode interference current Icmg becomes effective which results from the sum of the common-mode interference currents Icm1 and Icm2 of the two individual pulse converters 1 and 2: Icmg = Icm1 + Icm2. With a symmetrical design of the induction machine 3, the parasitic capacitances Cp33 and Cp34 of the winding systems 33, 34 are at least approximately equal, so that at equal voltages Uc33 and Uc34 and the two common-mode interference currents Icm1 and Icm2 are equal.

According to the invention, the two pulse converters 1, 2 are controlled by the drive devices 51, 52 or by the control device 5 in such a way that at their outputs 1 a, 1 b, 1 c or 2 a, 2 b, 2 c for the formation of the common mode currents Icm1 , Icm2 relevant potentials U1a, U1b, U1c or U2a, U2b, U2c at least approximately simultaneously connected to the winding systems 33, 34, that the voltage potentials Uc33, Uc34 over the parasitic capacitances Cp33, Cp34 of the winding systems 33, 34 to ground potential to each other are directed opposite and thus cancel the common mode interference currents ICm1 and Icm2 against each other.

This is achieved in the illustrated embodiment in that by opposing driving of the half bridges W1a, W1b and W1c of the inverter 1 to the half bridges W2a, W2b and W2c of the inverter 2, the output potentials U1a, U2a or U1b, U2b or U1c, U2c W2b in opposite directions change each other.

FIG. 4 shows in this regard on the basis of time diagrams an example of the course of the inverter output potentials U1a, U1b, U1c or U2a, U2b, U2c and the voltages Uc33, Uc34 on the parasitic capacitances Cp33, Cp34. Due to the opposite control of the half bridges W1a, W1b and W1c of the converter 1 to the half bridges W2a, W2b and W2c of the converter 2, the voltage changes Uc33, Uc34 over the parasitic capacitances Cp33 and Cp34 in opposite directions to each other, as in FIG. 4 can be seen on the basis of the temporal courses. Under the prerequisites of simultaneous switching operations in the converter half-bridges W1a, W2a or W1b, W2b or W1c, W2c and equally large capacitances Cp33 and Cp34, the common-mode currents Icm1 and Icm2 flowing via ground potential thus have the same amount, but are directed in the opposite direction, ie Icm1 = -Icm2. As a result, both currents Icm1 and Icm2 cancel each other out, ie in the DC voltage supply device 4, therefore, no common-mode interference current Icmg originating from the switching operations of the pulse converters 1, 2 becomes more effective. The same statement can be made if the sum of both voltages Uc33 + Uc34 is considered; it is zero at all times.

The formation of the switching times for controlling the pulse converter takes place in the in FIG. 3 and 4 illustrated embodiment again in an exemplary manner with the aid of a triangle auxiliary function UΔ in the sense of the known sine-wave modulation. For the pulse converter 1, a triangular auxiliary function UΔ1 = UΔ is compared in a known manner with the control voltages Ust1a = Usta, Ust1b = Ustb and Ust1c = Ustc determining the converter output in order to determine the switching times for the switches S1a, S1a '. , S1b, S1b 'and S1c, S1c'. The determination of the switching times for the pulse converter 2 takes place according to the same principle in the control device 52. In order to achieve a change in the switching states in the opposite direction to converter 1, the switching times of the switches S2a, S2a ', S2b, S2b' in the drive device 52 and S2c, S2c ', however, according to FIG. 4 formed from the inverse signals: UΔ2 = -UΔ1 = -UΔ; Ust2a = -Ust1a = -Usta; Ust1b = -Ust1b = -Ustb and Ust2c = -Ust1c = -Ustc. The formation of said inverse signals can, for example, with the aid of in FIG. 3 symbolically represented inverters 56, 57, 58 and 59.

Representative of the resulting inverter output voltages are in FIG. 4 Furthermore, the voltages U1ba and U2ba between the inverter output terminals 1a, 1b and 2a, 2b shown. As FIG. 4 shows, these are for the behavior of the machine relevant inverter output voltages due to the inverse drive also inverse to each other. Thus, both converters 1, 2 via the Wicklungssyteme 33, 34 preferably generate the same Grundschw ingungsphasenlagen the magnetic flux in the machine, it is therefore - as already mentioned - required that both winding systems 33, 34 are arranged offset by 180 ° to each other electrically.

The application of the solution according to the invention in drive systems with multi-phase pulse systems fed by multiphase pulsing converters thus does not result in any change in the function of the drive.
As already mentioned, the drive devices 51, 52 must be synchronized with each other so that in the respective half-bridges (W1a, W2b or W1b, W2a in the case of single-phase converters or W1a, W2a, W1b, W2b, W1c, W2b in the case of three-phase converters ) can give the same switching times. In the case of the exemplary use of a triangular auxiliary function UΔ in the sense of the known sine-triangle modulation, this is done by the triangular auxiliary function UΔ itself.
However, other online or offline modulation methods can also be used for driving the half-bridges (W1a, W2b or W1b, W2a for single-phase converters or W1a, W2a, W1b, W2b, W1c, W2b for three-phase converters); in this case, the synchronization is to be realized in another suitable way.
The signaling functions of the control device (5) or the drive devices (51, 52) are advantageously realized in at least one programmable hardware component, in particular LCA, and / or by software in a digital signal processing with at least one digital processor and / or executed as conventional hardware in analog and / or digital technology.

If the three-phase machine 3 is fed by more than two pulse converters 1, 2 from a common DC voltage supply 4, two of these pulse converters are each operated with the drive method according to the invention, so that the respective common mode signals generated by the two pulse converters each Cancel disturbing currents against each other.

If there are differences in the instantaneous values of the control voltages Ust1, Ust2 of the two pulse converters 1, 2, as described e.g. may be at different fundamental phase phases of three-phase machines, residues remain in the resulting common-mode interference current Icmg. The solution according to the invention can therefore be used particularly advantageously if in each case a pair of pulse converters 1, 2 generate the same or almost identical (or inverse) output voltages and thus winding phases 31, 32 or multi-phase winding systems 33, 34 with the same (or inverse) fundamental phase position be fed.

Such rotary field machines, which are designed in particular as synchronous machines which are excited in particular as rotor-side synchronous machines, can be designed for high drive power owing to the individual feeding of their winding strands or by using a plurality of multiphase winding systems, in particular e.g. for propulsion propulsion of a ship, in particular a submarine, is needed.

Claims (14)

1. Method for reducing common-mode interference currents in an electric drive system, having at least two pulse converters (1, 2) that are fed by a common DC power supply device (4) for feeding an electric polyphase machine (3) having at least two winding phases (31, 32) or at least two winding systems (33, 34), wherein at least two of the pulse converters (1, 2) in each case are respectively triggered by a control device (5) such that the potentials (U1a, U1b, U1c or U2a, U2b, U2c) that are decisive for the generation of common-mode currents (Icm1, Icm2) are applied in an at least approximately simultaneous manner to the winding phases (31, 32) affected by parasitic capacitances (Cp31, Cp32) or the winding systems (33, 34) of the polyphase machine (3) which are affected by parasitic capacitances (Cp33, Cp34), at the outputs (1a, 1b, 1c or 2a, 2b, 2c) of both pulse converters (1, 2), such that the voltage potentials (Uc31, Uc32 or Uc33, Uc34) are inverted relative to each other above the parasitic capacitances (Cp31, Cp32) of the winding phases (31, 32) or above the parasitic capacitances (Cp33, Cp34) of the winding systems (33, 34) in relation to the earth potential,
   characterised in that the triggering for each two pulse converters (1, 2) is realised by a modulation procedure with the help of triangular auxiliary functions, wherein the triangular auxiliary function (UΔ1) of one of each two pulse converters (1) is inverted compared to the triangular auxiliary function (UΔ2) of the other of each two pulse converters (2).
2. Method according to claim 1 for operating a polyphase machine (3) having a plurality of winding phases (31, 32) fed in terms of a single-winding power supply by one single-phase pulse converter (1, 2) in each case,
   characterised in that each two pulse converters (1, 2) are triggered by the control device (5), such that the instantaneous values of the output voltages (Ul, U2) of each two pulse converters (1, 2) are at least approximately equal.
3. Method according to claim 1 for operating a polyphase machine (3) having a plurality of multiphase winding systems (33, 34) fed by one multiphase pulse converter (1 or 2) each, characterised in that the winding systems (33 or 34) fed by each two pulse converters (1, 2) are arranged in the polyphase machine (3) so as to be electrically offset from one another by at least approximately 180° and each two pulse converters (1, 2) are triggered by the control device (5), such that the instantaneous values of the output voltages (U1ba, U1cb, U1ac) or (U2ba, U2cb, U2ac) of each two pulse converters (1, 2) are inverse to one another.
4. Method according to at least one of the preceding claims, characterised in that the triggering for each two pulse converters (1, 2) takes place with the aid of modulation procedures or pulse patterns working online and/or offline.
5. Electric drive system having at least two pulse converters (1, 2) fed from a common DC voltage supply device (4) for feeding an electric polyphase machine (3) having at least two winding phases (31, 32) or at least two winding systems (33, 34), in particular for the performance of the method according to one of claims 1 to 4,
   wherein at least in each case each two of the pulse converters (1, 2) have a switching dependency dependent on a control device (5), such that the potentials (U1a, U1b, U1c or U2a, U2b, U2c) that are decisive for the generation of common-mode currents (Icm1, Icm2) are applied in an at least approximately simultaneous manner to the winding phases (31, 32) affected by parasitic capacitances (Cp31, Cp32) or the winding systems (33, 34) of the polyphase machine (3) which are affected by parasitic capacitances (Cp33, Cp34), at the outputs (1a, 1b, 1c or 2a, 2b, 2c) of both pulse converters (1, 2), such that the voltage potentials (Uc31, Uc32 or Uc33, Uc34) are inverted relative to each other above the parasitic capacitances (Cp31, Cp32) of the winding phases (31, 32) or above the parasitic capacitances (Cp33, Cp34) of the winding systems (33, 34) in relation to the earth potential,
   characterised in that each two pulse converters (1, 2) can be triggered by a modulation procedure with the help of triangular auxiliary functions, wherein the triangular auxiliary function (UΔ1) of one of each two pulse converters (1) is inverted compared to the triangular auxiliary function (UΔ2) of the other of each two pulse converters (2).
6. Electric drive system according to claim 5, wherein the at least one polyphase machine (3) has a plurality of winding phases (31, 32) fed in terms of a single-winding power supply by a single-phase pulse converter (1, 2) in each case, characterised in that each two pulse converters (1, 2) have a switching dependency thanks to the control device (5), such that the instantaneous values of the output voltages (Ul, U2) of each two pulse converters (1, 2) are at least approximately equal.
7. Electric drive system according to claim 5, wherein the at least one polyphase machine (3) has a plurality of multiphase winding systems (33, 34) fed by one multiphase pulse converter (1 or 2) each,
   characterised in that the winding systems (33 or 34) fed by each two pulse converters (1, 2) are arranged in the polyphase machine (3) so as to be electrically offset from one another by at least approximately 180° and each two pulse converters (1, 2) have a switching dependency thanks to the control device (5), such that the instantaneous values of the output voltages (U1ba, U1cb, U1ac) or (U2ba, U2cb, U2ac) of each two pulse converters (1, 2) are inverse to one another.
8. Electric drive system (19) according to at least one of claims 5 to 7,
   characterised in that a common control device (5) is provided for each two pulse converters (1, 2) in each case.
9. Electric drive system according to at least one of claims 5 to 7,
   characterised in that a plurality of, in particular two, trigger devices (51, 52) which are linked to one another, in particular synchronised with one another in a device-related and/or functionally separate and suitably signal-related manner, are provided for each two pulse converters (1, 2) in each case.
10. Electric drive system according to at least one of claims 5 to 9,
    characterised in that signal-related functions of the control device (5) or of the triggering devices (51, 52) are realised in at least one programmable hardware module, in particular LCA, and/or by means of software in digital signal processing with at least one digital processor and/or are executed with conventional hardware in analogue and/or digital technologies.
11. Electric drive system according to at least one of claims 5 to 10,
    characterised in that one or more of the electric polyphase machines (3) is embodied as a synchronous machine with electric or permanent-magnetic excitation.
12. Electric drive system according to at least one of claims 5 to 10,
    characterised in that one or more of the electric polyphase machines (3) is embodied as an asynchronous machine.
13. Electric drive system according to at least one of claims 5 to 12,
    characterised in that one or more of the electric polyphase machines (3) is a propulsion drive of a ship, in particular a submarine.
14. Use of the electric drive system according to at least one of claims 5 to 13 in an electric on-board power supply system, in particular an electric DC on-board power supply system on ships, in particular on submarines.

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